A combination of high optical confinement and low internal optical loss is desired in laser diodes to achieve a high wall plug efficiency (WPE). Wall-plug efficiency is a common figure of merit defined as the ratio of the optical power output from the laser diode to the electrical power input into the laser diode. Optical power output may be diminished, for example, by internal optical losses, such as by absorption of photons by device layers or by current carriers within the device layers. High WPE may be achieved from structures having both low internal optical loss and high output optical loss. But high output optical loss requires high optical gain. If optical material gain is inherently limited by a chosen material, a large optical confinement factor is required to increase optical gain.
There remain ongoing needs for green-laser diode configurations that result in low internal optical loss, high optical gain, low series resistance, and reduced occurrence of misfit defects near the active region. In particular, there remain ongoing needs to determine optimal materials, layer structures, and dopant profiling within the layer structures so as to increase wall plug efficiencies.